import org.jspecify.annotations.Nullable;

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the

        TestIterator iterator = new TestIterator(null);

        // Verify iteration
        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertFalse(iterator.hasNext());

import org.jspecify.annotations.Nullable;

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the

import com.google.caliper.Param;
import com.google.common.base.Preconditions;
import java.util.Random;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests the speed of iteration of different iteration methods for collections.
 *
 * @author David Richter
 */
@NullUnmarked
public class MultisetIteratorBenchmark {
  @Param({"0", "1", "16", "256", "4096", "65536"})
  int size;

 * multimap.put(key1, baz);
 * }
 *
 * ... the iteration order for {@link #keys()} is {@code [key1, key2, key1]}, and similarly for
 * {@link #entries()}. Unlike {@link LinkedHashMultimap}, the iteration order is kept consistent
 * between keys, entries and values. For example, calling:
 *
 * {@snippet :
 * multimap.remove(key1, foo);
 * }
 *
 * <p>changes the entries iteration order to {@code [key2=bar, key1=baz]} and the key iteration

 * {@link #computeNext} method, and invoke the {@link #endOfData} method when appropriate.
 *
 * <p>Another example is an iterator that skips over null elements in a backing iterator. This could
 * be implemented as:
 *
 * {@snippet :
 * public static Iterator<String> skipNulls(final Iterator<String> in) {
 *   return new AbstractIterator<String>() {
 *     protected String computeNext() {
 *       while (in.hasNext()) {

 * need for a distinct {@code ImmutableBiMultimap} type.
 *
 * <p><a id="iteration"></a>
 *
 * <p><b>Key-grouped iteration.</b> All view collections follow the same iteration order. In all
 * current implementations, the iteration order always keeps multiple entries with the same key
 * together. Any creation method that would customarily respect insertion order (such as {@link

    } else {
      return RegularImmutableMultiset.create(entries);
    }
  }

  ImmutableMultiset() {}

  @Override
  public UnmodifiableIterator<E> iterator() {
    Iterator<Entry<E>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<E>() {
      int remaining;
      @Nullable E element;

      @Override
      public boolean hasNext() {

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import java.util.Set;
import org.jspecify.annotations.NullUnmarked;

/**
 * Very simple powerSet iteration benchmark.
 *
 * @author Kevin Bourrillion
 */
@NullUnmarked
public class PowerSetBenchmark {
  @Param({"2", "4", "8", "16"})
  int elements;

  Set<Set<Integer>> powerSet;

  @BeforeExperiment

     * with each iteration, so this algorithm takes O(log(digits)) iterations.
     *
     * We start out with a double-precision approximation, which may be higher or lower than the
     * true value. Therefore, we perform at least one Newton iteration to get a guess that's
     * definitely >= floor(sqrt(x)), and then continue the iteration until we reach a fixed point.
     */
    BigInteger sqrt0;
    int log2 = log2(x, FLOOR);